I'm not completely sure, but if you make a Contact object and add the phone number you want to call and then drop that object on your page then it could be possible that it works when you press the phone number.
And example on how to create a Contact can be found on example 9-15 of the Mobile Developer's Guide for Oracle Application Development Framework

Just an idea: in standard HTML a link such as &lt;a href="tel:1-847-555-5555"&gt;1-847-555-5555&lt;/a&gt; is parsed as a phone number by most smartphone browsers, so would a go link in the tel: format work in ADF Mobile?